122648 is the content object attribute ID, which you'll find in the "id" field in the "ezcontentobject_attribute" database table. The same ID is used in the "contentobject_attribute_id" field in the "ezbinaryfile" database table.

However how can I choose the right attribute id for my url knowing that I have various attribute id corresponding to the same object id ? In this exemple 13660 as 2 value for data-type_string= ezbinaryfile 122646 and 122648...?

Thanks a lot...I don't know a lot about ezpublish. I was looking in the admin backoffice and was looking how to export a set of pdf (we are moving content from an old website to a new one) and realized that it wasn't possible. So I was looking how to produce a list with the set's url and write a .bat file in order to download all the files according to their url. Perlhap's this is not the easiest way but I am actually working on Drupal and I don't know how to manage ezpublish well (I'm not a developer)...